Apparatus for electroslag remelting of consumable electrodes

ABSTRACT

The invention relates to the field of electrometallurgy, and in particular to an apparatus for electroslag remelting. The apparatus is characterized in that it has a transformer power supply means, which can be three-phase or which can consist of several single-phase transformers, the secondary windings of which are provided with center tappings which are interconnected through busbar conductors so as to provide for an equality of the line speeds of melting the electrodes and for a uniform temperature field within the slag bath. The invention can be utilized in the process of producing unique hollow or solid ingots and slabs of high-grade steels and alloys having a weight of 200 tons and higher.

United States Patent Paton et a1. 5] May 23, 1972 [54] APPARATUS FOR ELECTROSLAG 2,721,948 10/1955 Jordan ..13/9 UX hm TIN 3,128,411 4/1964 Persson... ..l3/9X gf k g S LE 3,143,699 8/1964 Russ ..13/9 X I O 3,344,839 10/1967 Sunnen 13/9 UX Inventors: Paton, Kotsjubin 3,410,946 Dillll'lg Ct skogo 9 kv Vladimir Konstantlnovich DIXOIl t Lebedev umsa Engelsa, 25, kv l2; Boris 1,983,544 12/1934 Ingelsrud ...13/12 hnflevkh Medovar, Bulvar Lesi Ukrainki 3,395,237 7/1968 Orton ..13/12 X 8; wadll'mvich FOREIGN PATENTS OR APPLICATIONS Zadorozhny pereulok, 3, kv. l4; Jury vadimovich Lamb, v d kh fl t k 1,545,017 9/1968 France "13/9 prospekt, 81 kv, 0 p 1,117,202 6/1968 Great Britain ..13/9 darenko, ulitsa Kreschatik, l5, kv. 34; v Mikhaihvich Baghi ulitsa Semash Primary Examiner-Bernard A. Gllheany R0 10 kv. 54/3; Nikolai vasmevich Assistant Examiner--R. N. Enval1,.1r. Podoh, umsa Pushkinskaya 8 12; Attorney-Lane, Aitken, Dunner & Ziems July Georglevich Emelyanenko, ulitsa Darvina, 5,1. 5, all of Kiev, U.S.S.R. [571 ABSTRACT [22] Filed, AP 8 1970 The invention relates to the field of electrometallurgy, and in particular to an apparatus for electroslag remelting. The ap- [21] App1.No.: 26,733 paratus is characterized in that it has a transformer power supply means, which can be three-phase or which can consist of several single-phase transformers, the secondary windings [30] Forelgn Appncamm Pmmty Dam of which are provided with center tappings which are inter- June 16, 1969 U.S.S.R ..1,336,305 nnec hr ugh bus r conductor so as to provide for an equality of the line speeds of melting the electrodes and for a [52] 11.8. C1 ..13/12 uniform temperature field Within the Slag bath- The invention 51 Int CL I 05, 3/ 0 can be utilized in the process of producing unique ho110w or 58 1 Field of Search.. ..13/12, 13 ES, 9 Solid ingots and Slabs of high-grade Steels and alloys having a weight of 200 tons and higher. [56] References Cited 23 Cl 9 Drawing Figures UNITED STATES PATENTS 1,127,475 2 /19l5 I Marshal1..... 319

Patented May 23, 1972 3,665,081

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Patented May 23, 1972 3,665,081

5 Sheets-Sheet INVENTORS BORIS E. PATON ef al APPARATUS FOR ELECTROSLAG REMELTING OF CONSUMABLE ELECTRODES BACKGROUND OF THE INVENTION The present invention relates to the field of electrometallurgy and, more particularly, to an apparatus for the electroslag remelting of consumable electrodes. The apparatus can be utilized to produce unique hollow or solid ingots and slabs having a weight of up to 200 tons and higher.

Apparatus for electroslag remelting consumable electrodes are known in the art. For example, a bifilar (two-electrode) apparatus comprising a mold, an electrode holder with electrodes fixedly secured therein with respect to each other, which electrodes are insulated one from another and are fed from one single-phase transformer is known (cf. the USSR Author's Certificates No. 2198, cl. 18B 5/56 and No. 2594, cl. l 83 5/56 which correspond to French Pat. No. 1,545,017). As explained in the corresponding French patent and in an earlier filed Great Britain Pat. No. l I 17202 at page 3, lines 95-106, a bifilar arrangement of parts is accomplished by the parallel and close spacing of the current conductors. This arrangement results in electrical compensation of the magnetic fields produced by high current AC. power, decreases the inductive reactance, and considerably increases the power factor (Cos Also known in the art are three-electrode electroslag remelting furnaces fed either from one three-phase transformer of from several single-phase transformers (cf. the book Electroslag Remelting by 8.1. Medovar et al. p. 21, "Mettalurgizdat Publishers, Moscow, 1963).

Such apparatus make it possible to produce high-quality metal in ingots having weights of to tons. in this case the pan or bottom plate of the electroslag remelting furnace mold must be connected either to the neutral point (in a threephase furnace) or to the center tapping of the secondary winding of the transformer (in a single-phase furnace) in order to provide an equality of the line speeds of melting for electrodes having different melting temperatures, different cross sections or a change in the geometry of their disposition in the slag bath. The lower end portions of the electrodes are immersed in the slag bath by a common crosspiece and the equality of line speeds of melting is particularly important at a low depth of the bath which is sometimes required by the process conditions. The single phase can be supplemented by an equalizing reactor or choke connected in parallel to the transformer in the bifilar furnaces. The provision for equality of the line speeds of melting allows for the trouble-free operation of the apparatus.

When the weight of the ingot to be cast is increased to 100 tons, preference is given to multielectrode circuits, for example those containing four-electrodes, six-electrodes and higher.. Such apparatus having input power of higher than 10,000 KVA are to be fed not from a single three-phase transformer but from several single-phase transformers, which are inserted into the three-phase mains with their primary windings and are located symmetrically relative to the geometrical center of the furnace in order to obtain the shortest possible dimensions and a full symmetry for the power network of the apparatus. For lower ingot tonnage apparatus, one three-phase transformer can be used.

The remelting of four, six and more consumable electrodes, secured in a common crosspiece of such an apparatus necessitates a provision for maintaining equality in the line speeds of melting of the consumable electrodes, because in the process of casting the electrodes having a weight of to 50 tons, and higher, they will inevitably be affected by pores and cavities, i.e., there will be differences in the electrodes sections. Furthermore, the geometry of disposition of the electrodes relative to the symmetry axis of the mold may be disturbed, and this will cause an unbalanced melting condition for the electrodes or even the end portion of some of the electrodes can melt sufficiently so they can become located on the surface of the slag bath and/or the immersion of the end portions of other electrodes into the slag bath to a position resulting in a short circuit with the face of the underlying metal pool. This leads to emergency operating conditions of the apparatus.

The known methods of elimination of the unbalance in the line speeds of melting of electrodes having different cross-sections in high-power electroslag remelting apparatus, for example by means of the connection of the pan or bottom plate of the apparatus with the neutral point of the star" formed by the secondary windings of three transformers, are not suitable for large tonnage furnaces since in this case the neutral wire has a considerable inductive resistance due to the fact that such a circuit cannot provide for a fully compensated noninductively charged current conductor. Therefore, the effectiveness of the neutral wire is very low and all the undesirable phenomena mentioned above are quire possible to appear in the process of melting.

An object of the present invention is to eliminate the abovementioned disadvantages.

BRIEF SUMMARY OF THE INVENTION The principal object of the invention is to provide an apparatus for electroslag remelting of an even number of, not less than four, groups of consumable electrodes which makes possible the production of high-quality metal ingots weighing tons and higher and to completely eliminate the efiect of the above-mentioned unbalanced conditions in melting the consumable electrodes, independent of the reasons of their appearance as well as to eliminate emergency operating conditions.

This object is attained by providing an apparatus for the electroslag remelting of consumable electrodes including a mold and an electrode holder for securing in fixed position relative to one another an even number of not less than four groups of electrodes, each group consisting of at least one electrode. When the groups consist of one electrode each, the electrodes are insulated one from another. A power transformer means is provided in which the total number of the secondary windings is one-half the number of the groups of electrodes, each secondary winding being connected to two different groups of electrodes. According to the invention, the center tappings of the secondary windings of the transformer are interconnected through busbar conductors insulated from the construction members of the apparatus. This provides for an'equality of the line speeds of melting the electrodes and establishes a uniform temperature field within the slag bath.

In order to provide a fully compensated noninductive current-supply line to the electrodes, each of the busbar conductors connecting the center tapping of one secondary winding of the transformers with the center tappings of the remaining secondary windings is preferably placed in bifilar arrangement with respect to the busbar conductors connecting the terminals of this secondary winding to the groups of electrodes. The junction point or connection of all the center tappings of the secondary windings is preferably positioned on the symmetry axis of the electrode holder.

To provide for an increase in the efficiency of stabilization of the line speeds of melting of the electrodes, the groups of electrodes are preferably located at the apices of a regular polygon so that each two groups of electrodes connected to the terminals of any one secondary winding of the transformer is located either at two adjacent apices of the polygon formed by the arrangement of the electrodes.

In order to increase the coefficient of filling the mold and to reduce the height of the apparatus, it may be equipped with a metal blank mounted in the central part of the electrode holder and electrically insulated therefrom, one end of the blank being connected to the junction of the busbar conductors from the center tappings of the secondary windings of the transformer means. By this manner of electrical connection the metal blank is connected to the power supply through a normally neutral center tapping circuit rather than being directly connected to the normal power circuit of the secondary windings as in the case of the electrodes. The metal blank may be composed of metal which differs from that of the consumable electrodes by a chemical composition when additional alloying of the ingot is desired.

Furthermore, the apparatus may be provided with an equalizing reactor or choke connected in parallel to each secondary winding of the transformer, the center tapping of this reactor being connected with the center tappings of the other equalizing reactors connected to the remaining secondary windings of the transformer.

The apparatus made according to the present invention successively solves all the problems above-mentioned.

Further objects and advantages of the invention will be apparent from the following detailed description of some specific embodiments of the invention, reference being made to the accompanying drawings, in which:

FIG. 1 is an electric circuit diagram of the apparatus, for remelting of four consumable electrodes (defined as four groups of electrodes), in which the center tappings of the secondary windings of the two transformers are interconnected through a busbar conductor;

FIG. 2 is an electric circuit diagram of the apparatus, for remelting four consumable electrodes, in which the interconnected center tappings are taken from two equalizing reactors provided in parallel with each of the two transformers;

FIG. 3 is an electric circuit diagram of the apparatus, for casting hollow ingots from 16 groups of electrodes, in which the center tappings of the secondary windings of the transformers (eight) are interconnected in the center of the electrode holder;

FIG. 4 is an electric circuit diagram of the apparatus, for remelting six consumable electrodes (six groups), in which the secondary windings of the transformers are connected with two electrodes disposed at two adjacent apices of a hexagon;

FIG. 5 is a vector diagram of voltages between the electrodes in the circuit shown in FIG. 4;

FIG. 6 is an electric circuit diagram of the apparatus for remelting six consumable electrodes, in which the secondary windings of the transformers are connected with two electrodes disposed at diametrically opposite apices of a hexagon;

FIG. 7 is a vector diagram of voltages between the electrodes of the apparatus shown in FIG. 6;

FIG. 8 (on the sheet with FIG. 3) is an electric circuit diagram of the apparatus for remelting six consumable electrodes, in which the center tappings of the equalizing reactors are connected with a metal blank; and

FIG. 9 is a furnace and electrical diagram of the apparatus shown in FIG. 1.

DETAILED DESCRIPTION Referring to the circuit diagram of the apparatus illustrated in FIG. 1, four groups of consumable electrodes I, II, III and IV are secured in a fixed position relative to one another in a common electrode holder (not shown) and are subjected to electroslag remelting. Each electrode group consists of a single electrode. The consumable electrodes are connected in pairs to the two terminals of each of the secondary windings of the two transformers 5, 6. The electrodes I and II are respectively connected to the terminals 1! and 2 of the secondary winding of the transformer 6, while the electrodes III and IV are connected to the terminals 3 and 4 of the secondary winding of the transformer 5. The center tappings 0,, of the secondary windings of the transformers and 6 are interconnected by a busbar conductor 7 which is insulated from the mold 8 and from the other members of the construction of the apparatus. In this case the primary windings of the transformers 5 and 6 may be connected to any of the phases of the three-phase main. The connection of the center tappings 0,, 0 of the secondary windings of the transformers 5, 6 through the common busbar conductor 7 provides for a required electric coupling between all the electrode groups I, II, III, IV and ensures active self-control of the line speeds of melting the consumable electrodes.

When it is technologically difficult to tap out the center point of the secondary windings of the transformers, equalizing reactors or chokes may be used for this purpose. As shown in FIG. 2, in this case, the groups of electrodes I, II, III and IV are also connected in pairs to the terminals of the secondary windings of the transformers 5 and 6. The electrodes I and II are connected to the terminals 1 and 2, while the electrodes III and IV are connected to the terminals 3 and 4 and equalizing reactors or chokes 9 and 10 are connected in parallel to the secondary windings of the transformers 5 and 6, respectively. The center tappings 0, and 0 of the equalizing reactors 9 and 10 are interconnected by a busbar conductor 7 which is also insulated from the members of the construction of the apparatus.

When operating an apparatus with a large number of groups of electrodes, the use of the shortest electrical connectors for the power network becomes a stringent requirement both for increasing technical and economical characteristics of the apparatus as well as for providing for its working capacity on heavy currents, it is necessary to provide for a fully compensated noninductive current conductor supplying power to the consumable electrodes. This object is attained in a general case of an electric supply circuit for the apparatus shown in FIG. 3. This apparatus is used for casting hollow ingots by remelting consumable electrodes with an even number of groups of electrodes n 2 m (where m 2, 3, 4, 5,...), the groups of electrodes I, II, III, IV, V, VI,A and B being connected in pairs to the terminals of the secondary windings 1, 2, 3, 4, 5, 6', a, b, etc., of the transformers whose number is one-half that of the n groups. The center tappings 0,, 0 0 0,,, etc. of the secondary windings are interconnected through the busbar conductors 7, each conductor being placed in bifilar arrangement to the busbar conductors connecting the ends of the corresponding secondary windings with two groups of electrodes.

The point of connection 11 of all the center tappings of the secondary windings of the transformers is located directly in the electrodes holder along the symmetry axis of the molds 12 and 13 and is electrically insulated therefrom. The secondary windings of these transformers may be connected to a singlephase or three-phase mains either with a cyclic alternation of phases in the direction of the bypass of the mold or with a phase alternation according'to any preselected law.

A complete rendering of FIG. 3, as is apparent, will illustrate eight transformers with 16 groups of electrodes (I XVI), each group including two electrodes.

For increasing the efficiency of the self-stabilization of the line speeds of melting of the electrodes in the apparatus when highly powered, the groups of consumable electrodes are disposed at the apices of a regular polygon, in which case the two groups of electrodes connected to the terminals of one secondary winding of the transformer are located either at two adjacent apices or at two diametrically oppositeapices of the said polygon.

All further embodiments of the invention are illustrated on the apparatus shown in FIG. 4 wherein the apparatus has six groups of consumable electrodes, I, II, III, IV, V, VI fixedly secured relative to each other and insulated from each other. The groups of electrodes are supplied with current from three single-phase transformers 14, 15, 16 connected to three-phase mains. In this case each electrode group has one electrode. When only six consumable electrodes are used in the system, the apparatus can be supplied from one three-phase transformer, having three secondary windings.

The consumable electrodes I, II, III, IV, V, VI are located at the apices of a regular polygon and form three pairs of electrodes I-II, Ill-IV, V-VI which are respectively connected in series to the secondary windings 1 2, 3, 4, 5 ,6 of three single-phase transformers, each being disposed at an angle of to the symmetry axis of the apparatus. The simplest structure of network having short conductors, which is very important during the operation of the apparatus on heavy currents (from 50 to 70 kA), is obtained if each of the pairs of the electrodes I-Il, III-IV, V-VI is disposed at two apices of a hexagon formed by the electrodes belonging to one face of the hexagon, while the junction point or connection 11 of all the center tappings of the transformers is located on the symmetry axis of the electrode holder. In this case a minimum inductance of the entire network of the apparatus is obtained because each of the busbar conductors 7 connecting the center tappings of the secondary windings of the power supply transformers is placed in bifilar arrangement to the busbar conductors connecting the terminals of the secondary windings of the corresponding transfonner to the electrodes of the apparatus.

FIG. 5 shows a vector diagram of voltages between the electrodes I, II, III, IV, V, VI arranged in the circuit shown in FIG. 4. The connection of all the center tappings provides for the required electric coupling between the electrodes and transformers as well as for active self-control of the line speed of melting the electrodes. The center tappings of all the secondary windings have the same potential and are shown in the diagram by the point 11 which divides all line voltages U rn-m r-n When it is assumed that all of the electrodes are immersed into a slug bath at the same depth, then the voltages, for example between the electrode VI and the other electrodes, according to the voltage diagram, are equal, therefore where U is a line voltage. In this case, the equivalent resistances of the slag between the end of each electrode and the molten metal bath are equal, therefore, the currents passing through each of the electrodes are also equal. Now suppose that the electrode VI becomes immersed into the slag deeper than the other electrodes due to a difference in a cross section thereof or due to a disturbance of the geometry of disposition of the electrodes in the slag bath or due to a different melting temperature of the electrodes. In this case, the resistance between the end of the immersed electrode VI and the molten metal bath is lower than the resistance between the ends of the other electrodes and the metal, due to the fact that each of the electrodes I, II, III, IV, V] acquires a certain current increment A J determined by the voltage and resistance between the electrode VI and each of the electrodes, which are geometrically summed up in the electrode VI. Therefore, the electrode VI is melted more rapidly than the remaining electrodes and the depth'of immersion of the electrodes into the slag bath is brought into balance. If the cause of the unbalance in melting the electrodes is invariable during the whole period of melting, the depth of immersion of the electrode VI will be somewhat larger than that of the other electrodes. This difference in the depths of immersion depends on improved gain factor realized by the whole system of slag-control described herein.

The circuit of the apparatus shown in FIG. 4 features some assymetry of voltages; the electrode VI with the electrode V have a voltage U, U and U ='U/2, as has each of the electrodes, i.e., the voltage between the electrodes is not pro-, portional to the distances therebetween. Therefore, in order to provide a full symmetry, of the diagram of voltages betweenall the electrodes and to increase the effectiveness of stabilization of the line speeds of melting the consumable electrodes, each pair of the electrodes say III-VI, connected to the same secondary windings 3', 6 of the transformers 14 may be connected at two opposite apices of the regular hexagon as shown by FIG. 6, In this case, the vector diagram of voltages between the electrodes shown in FIG. 7 completely follows the geometry of disposition of the electrodes in the slag bath, in which case the voltages between any adjacent electrodes, for example l-II, lI-III, IIIIV, etc., are equal and amount U/2; the voltage between the electrodes disposed at the apices of the equilateral triangles (for example A II, IV, V] or Al, Ill, V) are also equal and amount to V the voltages between the electrodes disposed at the opposite apices of the hexagon U r-n n. r-nequal and come to U i.e., there is provided a full symmetry of voltages as the voltages between the electrodes rise in proportion to the distances therebetween, therefore, the effectiveness of selfcontrol is higher as compared to the circuit shown in FIG. 4.

To increase the coefiicient of filling of the mold and to reduce the height of the apparatus, a metal blank insulated from the members of the construction of the apparatus can be positioned in the center of the regular polygon formed by the consumable groups of electrodes I-VI. The lower end of the metal blank is then immersed in the slag bath. The center tappings of the secondary windings of the transformers or equalizing reactors may be either connected to the said metal blank or be insulated therefrom. Shown in FIG. 8 is an electric circuit diagram of an apparatus for remelting in a cooled mold of six consumable electrodes I-Vl disposed at the apices of a regular hexagon and divided in pairs I-lI-IIl-IV-V-Vl, each being correspondingly connected to the terminals 1, 2', 3', 4', 5 6 of the secondary windings of three single-phase transformers 14, 15, 16 whose primary windings are connected to three-phase mains. Connected to the terminals of each secondary winding 1', 2', 3, 4, 5, 6 is a winding of an equalizing reactor respectively l8, 19, 20. The center tappings 0,, 0 0 of the reactors are interconnected with busbars conductors 7, the junction point of all the busbar conductor being connected to a consumable metal blank 17, which is located in the center of the hexagon. The lower end of the blank is immersed into the slag bath for melting by the molten slag. The operating principle of the apparatus shown in FIG. 8 is similar to that described above.

FIG. 9 shows the arrangement of the furnace and the two transformers 5 and 6 of FIG. 1. The busbar conductor 7 is shown interconnecting center tappings 0 and 0 Electrode groups I, II, III, IV are insulated from each other by insulation 7a retained in electrode holder 7b. The electrodes are melted in slag bath 8a provided in cooled mold 8 and the melted metal collects in the molten metal pool 8b and then solidifies to form a high quality ingot 80.

Thus, the proposed apparatus makes it possible to carry out the process of electroslag remelting of any even number, but not less than four, groups of consumable electrodes fixedly secured in a common electrode holder with respect to each other and having different cross sections, different melting temperatures, or a different chemical composition. The apparatus corrects for disturbances of the geometry of disposition of the electrodes in a slag bath. Through use of the apparatus it is possible to completely eliminate the unbalance in the character of melting of the electrodes and to avoid the possibility of occurrence of the emergency operating conditions.

It is clear that in case of a great number of transformers and considerable distances between the electrodes, for example during the casting of a hollow ingot having a large diameter or a rectangular ingot-slab, it is possible to connect the center tappings of the transformer windings or the center tappings of the equalizing reactors into groups, each group having at least two windings. In this case there is no electric coupling of the pan or bottom plate and the ingot with the power source through the electrodes, and this significantly simplifies the construction of the apparatus particularly when casting the ingots weighing more than tons and when casting the hollow ingots.

Furthermore, in the proposed apparatus, due to the presence of voltages between all the electrodes, there is provided a current through the slag between these electrodes, and this leads to creation of a uniform temperature field within the slag bath. This is especially important for casting of large shaped ingots.

We claim:

1. An apparatus for electroslag remelting comprising: a plurality of consumable electrodes; a mold for the formation of an ingot from remelted electrode metal in a molten slag bath;

an electrode holder for securing said electrodes in fixed position relative to one another, and at least one transformer means for supplying power to said electrodes; said electrodes comprising an even number of at least four directly powered groups of consumable electrodes, each of said groups containing at least one electrode, each of said groups of electrodes being insulated one from another, the total number of secondary windings of said transformer means being one-half the number of groups of said electrodes, each of said secondary windings being respectively connected to two different groups of said electrodes and each of said secondary windings being provided with center tapping means including center tappings, and all of said center tappings are interconnected to each other and are insulated from the other elements of said apparatus, whereby an equality of the line speeds of melting said electrodes and a uniform temperature field in said slag bath are obtained.

2. An apparatus as claimed in claim 1, in which all of said center tappings of said center tapping means are interconnected through busbar conductors, and in which each said busbar conductor for each said winding is in bifilar arrangement to the connections between the terminals of the associated said secondary winding and the groups of electrodes powered thereby, and in which the connection junction of all the center tappings of the secondary windings of said transformer means is located on the symmetry axis of said electrode holder to provide for a noninductive current conductor arrangement to the electrodes.

3. An apparatus as claimed in claim 1, in which said groups of electrodes are horizontally disposed and define a regular polygon spacing configuration wherein each of said groups of electrodes is disposed at an apex of the polygon configuration, and in which each two groups of electrodes connected with the terminals of one secondary winding of said transformer means are disposed at two adjacent apices of said polygon configuration.

4. An apparatus as claimed in claim 1, in which said groups of electrodes are disposed at the apices of a regular polygon formed thereby, and in which each two groups of electrodes connected to the terminals of one secondary winding of the transformer are disposed at the diametrically opposite apices of said polygon.

5. An apparatus as claimed in claim 1, in which a metal blank having two ends is mounted in the central part of said electrode holder and is insulated therefrom, one end of said blank being immersed into said slag bath and the other end thereof being connected to said busbar conductors from the connection junction of the center tappings of said transformer means.

6. An apparatus as claimed in claim 5, in which said metal blank is of a different chemical composition from that of the metal of the consumable electrodes, whereby additional alloying of the ingot is provided.

7. An apparatus as claimed in claim 1, in which each said center tapping means includes an equalizing reactor connected in parallel to the associated secondary winding of said transformer means, the center tapping of each reactor being interconnected with the center tappings of the other equalizing reactors connected to the remaining secondary windings of said transformer means.

8. An apparatus for electroslag remelting, comprising: a plurality of consumable electrodes, a mold for the formation of an ingot from remelted electrode metal in a molten slag bath, an electrode holder means providing for the simultaneous movement of said electrodes, and a power supply means connected to said electrodes, said electrodes comprising an even number of at least four directly powered groups of consumable electrodes, each group containing at least one electrode,

each of said groups of electrodes being insulated from one another, said power supply means including a plurality of discrete supply means for powering groups of electrodes less than the total number of said groups, each discrete supply means being connected to directly supply power to a different set of two of said groups, and electrical connection means interconnecting at least two of said discrete supply means to promote equality of the line speeds of melting of said plurality of electrodes.

9. An apparatus according to claim 8, in which said electrode holder means secures said electrodes in fixed position relative to one another.

10. An apparatus according to claim 8. in which said power supply means comprises transformer means in which the total number of secondary windings is one-half the number of groups of electrodes.

11. An apparatus according to claim 10, in which each of said secondary windings is respectively connected to two different groups of said electrodes.

12. An apparatus according to claim 10, in which said electrical connection means interconnecting said discrete supply means comprises interconnected center tapping means, including center tappings, from at least two secondary windings.

13. An apparatus according to claim 12, in which said electrical connection means comprises interconnected center tappings from all said secondary windings.

14. An apparatus according to claim 12, in which said interconnected center tappings are electrically insulated from the other elements of said apparatus.

15. An apparatus according to claim 12, in which said interconnected center tappings are electrically connected to a consumable metal blank adapted to have one end thereof immersed into the molten slag bath.

16. An apparatus according to claim 15, in which said metal blank is held by said electrode holder means.

17. An apparatus according to claim 10, in which said groups of electrodes are disposed at the apices of a regular polygon configuration formed thereby, and in which each two groups of electrodes connected with the terminals of one secondary winding of said transformer means are disposed at two adjacent apices of said polygon.

18. An apparatus according to claim 10, in which said groups of electrodes are disposed at the apices of a regular polygon configuration formed thereby, and in which each two groups of electrodes connected to the terminals of one secondary winding of the transformer are disposed at the diametrically opposite apices of said polygon.

19. An apparatus according to claim 12, in which an equalizing reactor is connected in parallel to each secondary winding of said transformer means, the center tappings of at least two reactors being interconnected.

20. An apparatus according to claim 19, in which the center tappings of all reactors are interconnected.

21. An apparatus according to claim 12, in which each of said center tappings of said center tapping means are interconnected through busbar conductors, and in which each said busbar conductor for each said winding is in bifilar arrange ment to the conductors between the terminals of the associated said secondary winding and the groups of electrodes powered thereby.

22. The apparatus according to claim 13, in which the connection junction of said interconnected center tappings is located on the symmetry axis of said electrode holder means to provide for a noninductive current conductor to the electrodes.

23. The apparatus according to claim 8, in which each group of directly powered consumable electrodes contains at least two electrodes.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,665,081 Dated May 23, 1972 I lnventofls) BOIlS Evgenlevlch Paton et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 29, "of" should read or line ,30, "Mettalurgizdat" should-read Metallurgizdatv Column 2, line 6, "quire" should read a quite Signed and sealed this 3Id d 8.y of October 1972.

(SEAL) Attest:

EDWARD M.FLETCHER,JR.. ROBERT GOTTSCHALK AttestingOfficer Commissioner of Patents USCOMM-DC 603764 69 U.S. GOVERNMENT PRINTING OFFICE: I9! o-ass-au,

FORM PO-IOSO (10-69) UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTlON Patent NO. 3,665 ,081 Dated May 23, 1972 Inventor) Boris Evgenievlch Paton et a1 It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Column 1, line 29, "of" should read or line 30, "Mettalurgizdat" should read Metallurgizdat Column 2, line 6, "quire" should read quite Signed and sealed this 3rd day of October 1972.

(SEAL) Attest:

EDWARD M.PLETCHER,JR. ROBERT GOTTSCHALK Attesting Officer Commissioner of Patents ORM (10459) USCOMM-DC scan-ps9 U.S. GOVERNMENT PRINTNG OFFICE 1 959 0-356-335- 

1. An apparatus for electroslag remelting comprising: a plurality of consumable electrodes; a mold for the formation of an ingot from remelted electrode metal in a molten slag bath; an electrode holder for securing said electrodes in fixed position relative to one another, and at least one transformer means for supplying power to said electrodes; said electrodes comprising an even number of at least four directly powered groups of consumable electrodes, each of said groups containing at least one electrode, each of said groups of electrodes being insulated one from another, the total number of secondary windings of said transformer means being one-half the number of groups of said electrodes, each of said secondary windings being respectively connected to two different groups of said electrodes and each of said secondary windings being provided with center tapping means including center tappings, and all of said center tappings are interconnected to each other and are insulated from the other elements of said apparatus, whereby an equality of the line speeds of melting said electrodes and a uniform temperature field in said slag bath are obtained.
 2. An apparatus as claimed in claim 1, in which all of said center tappings of said center tapping means are interconnected through busbar conductors, and in which each said busbar conductor for each said winding is in bifilar arrangement to the connections between the terminals of the associated said secondary winding and the groups of electrodes powered thereby, and in which the connection junction of all the center tappings of the secondary windings of said transformer means is located on the symmetry axis of said electrode holder to provide for a noninductive current conductor arrangement to the electrodes.
 3. An apparatus as claimed in claim 1, in which said groups of electrodes are horizontally disposed and define a regular polygon spacing configuration wherein each of said groups of electrodes is disposed at an apex of the polygon configuration, and in which each two groups of electrodes connected with the terminals of one secondary winding of said transformer means are disposed at two adjacent apices of said polygon configuration.
 4. An apparatus as claimed in claim 1, in which said groups of electrodes are disposed at the apices of a regular polygon formed thereby, and in which each two groups of electrodes connected to the terminals of one secondary winding of the transformer are disposed at the diametrically opposite apices of said polygon.
 5. An apparatus as claimed in claim 1, in which a metal blank having two ends is mounted in the central part of said electrode holder and is insulated therefrom, one end of said blank being immersed into said slag bath and the other end thereof being connected to said busbar conductors from the connection junction of the center tappings of said transformer means.
 6. An apparatus as claimed in claim 5, in which said metal blank is of a different chemical composition from that of the metal of the consumable electrodes, whereby additional alloying of the ingot is provided.
 7. An apparatus as claimed in claim 1, in which each said center tapping means includes an equalizing reactor connected in parallel to the associated secondary winding of said transformer means, the center tapping of each reactor being interconnected with the center tappings of the other equalizing reactors connected to the remaining secondary windings of said transformer means.
 8. An apparatus for electroslag remelting, comprising: a plurality of consumable electrodes, a mold for the formation of an ingot from remelted electrode metal in a molten slag bath, an electrode holder means providing for the simultaneous movement of said electrodes, and a power supply means connected to said electrodes, said electrodes comprising an even number of at least four directly powered groups of consumable electrodes, each group containing at least one electrode, each of said groups of electrodes being insulated from one another, said power supply means including a plurality of discrete supply means for powering groups of electrodes less than the total number of said groups, each discrete supply means being connected to directly supply power to a different set of two of said groups, and electrical connection means interconnecting at lEast two of said discrete supply means to promote equality of the line speeds of melting of said plurality of electrodes.
 9. An apparatus according to claim 8, in which said electrode holder means secures said electrodes in fixed position relative to one another.
 10. An apparatus according to claim 8, in which said power supply means comprises transformer means in which the total number of secondary windings is one-half the number of groups of electrodes.
 11. An apparatus according to claim 10, in which each of said secondary windings is respectively connected to two different groups of said electrodes.
 12. An apparatus according to claim 10, in which said electrical connection means interconnecting said discrete supply means comprises interconnected center tapping means, including center tappings, from at least two secondary windings.
 13. An apparatus according to claim 12, in which said electrical connection means comprises interconnected center tappings from all said secondary windings.
 14. An apparatus according to claim 12, in which said interconnected center tappings are electrically insulated from the other elements of said apparatus.
 15. An apparatus according to claim 12, in which said interconnected center tappings are electrically connected to a consumable metal blank adapted to have one end thereof immersed into the molten slag bath.
 16. An apparatus according to claim 15, in which said metal blank is held by said electrode holder means.
 17. An apparatus according to claim 10, in which said groups of electrodes are disposed at the apices of a regular polygon configuration formed thereby, and in which each two groups of electrodes connected with the terminals of one secondary winding of said transformer means are disposed at two adjacent apices of said polygon.
 18. An apparatus according to claim 10, in which said groups of electrodes are disposed at the apices of a regular polygon configuration formed thereby, and in which each two groups of electrodes connected to the terminals of one secondary winding of the transformer are disposed at the diametrically opposite apices of said polygon.
 19. An apparatus according to claim 12, in which an equalizing reactor is connected in parallel to each secondary winding of said transformer means, the center tappings of at least two reactors being interconnected.
 20. An apparatus according to claim 19, in which the center tappings of all reactors are interconnected.
 21. An apparatus according to claim 12, in which each of said center tappings of said center tapping means are interconnected through busbar conductors, and in which each said busbar conductor for each said winding is in bifilar arrangement to the conductors between the terminals of the associated said secondary winding and the groups of electrodes powered thereby.
 22. The apparatus according to claim 13, in which the connection junction of said interconnected center tappings is located on the symmetry axis of said electrode holder means to provide for a noninductive current conductor to the electrodes.
 23. The apparatus according to claim 8, in which each group of directly powered consumable electrodes contains at least two electrodes. 